Re: [asa] Speciation

Randy,

I wasn't being specific enough. I hope this is slightly more clear
(although it may not be any more correct?).

I was thinking of cases where there is an increase of complexity due to
mutation.
That would be an organism exhibiting first expression.

Here's an example taken from berkeley.edu:

[quote]
*Mutation*
A mutation <javascript:Glossary('Mutation',1)> could cause parents with
genes for bright green coloration to have offspring with a gene for brown
coloration. That would make the genes for brown beetles more frequent in the
population.
[unquote]

Of course you are correct that allopatric speciation, for example, (where a
population becomes isolated) can speciate because a trait is lost in one of
the populations and 100% of that population is missing the trait.

If the lack of that trait means that population could not reproduce with
the other population when the two populations are combined then speciation
would have occurred (but without any "first organism" - so you are correct
about that in this case). May I point out that would be starting with the
same information in both populations and one population would lose
information? That doesn't explain the ascent of more complex organisms.
For that we need mutations.

[quote from another page on berekely.edu]
*So we meet again:* When another storm reintroduces the island flies to the
mainland, they will not readily mate with the mainland flies since they’ve
evolved different courtship behaviors. The few that do mate with the
mainland flies, produce inviable eggs because of other genetic differences
between the two populations. The lineage has split now that genes cannot
flow between the populations.
[unquote]

So, what I was thinking of was/is really the case where a mutation adds new
information to one of the populations (group B) and the resulting new trait
(brown color) spreads throughout 100% of the B population. In this case one
population has brown members and the other does not. In that case the
organism with the mutation is an original unique first organism. But it is
also true that population A and population B still have common ancestors.
But if they (the two populations) truly cannot reproduce together then it
is obvious the speciated population cannot breed with its own predecessor
species.

Of course it is really more complicated because population B may have both
green and brown genes for a long time. But if allopatric speciation then
happens because all the carriers of "green genes" die off , then all the
members of group B will be brown forever.

My understanding is a long accumulation of many many mutations can cause
complexity to accumulate until one day what is seen is a new organism with
new capabilities. What I don't know is whether the speciation could occur
before the expression of these capabilities. I don't see why not.

When we get an organism that expresses a gene and that trait has highly
selective advantage then that organism and all its descendants allegedly
reproduce at a higher rate than than those who don't express the gene. This
is probably quite important. In a highly competitive world the more capable
species might push out its competitors ecologically.

I agree the biologists can say all this much better than I can.

Thanks,
Dave C

On Sun, Oct 4, 2009 at 7:33 PM, Randy Isaac <randyisaac@comcast.net> wrote:

> Isn't it correct to say that every act of reproduction leads to offspring
> that are members of the same species as the parents? And yet, speciation
> does occur. The significance is that there is seldom, if ever, a "first" of
> any species, not just humans. So it seems that there is never a first
> organism, in the sense of a first of a species. As always, the exceptions
> prove the rule. Any time a single mutation event is sufficient to generate
> differentiation for a new species, the rule would be broken. Perhaps the
> biologists on this list can tell us how often that occurs.
>
> Randy
>
>
>
> David wrote:
>
>
> Seems to me you have roughly described speciation in general. This is why
> it puzzled me so much when someone asserted here that there wasn't a first
> human. There is always a first organism.
>
>

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Received on Sun Oct 4 23:27:27 2009